41 merc heater

[Jim in Wisconsin]

My friend's 41 Merc has a hot air heater and we were wondering if it is factory installed - dealer installed - or what. It certainly appears to be original and is a real nice unit. The exhaust pipe on the right side goes into a cast iron heat exchanger. There is a blower motor under the hood and a duct going into the cab. The control is mounted under the dash on a cast aluminum bracket. We haven't seen any brand names on it (like South Wind or something).
Has anyone seen these or know more about it?
Thanks
Jim S.

 

[waterboychuck]

Photos of the unit would be great.